Asexual and sexual replication in sporulating organisms

This paper develops models describing asexual and sexual replication in sporulating organisms. Replication via sporulation is the replication strategy for all multicellular life, and may even be observed in unicellular life (such as with budding yeast). We consider diploid populations replicating via one of two possible sporulation mechanisms: (1) Asexual sporulation, whereby adult organisms produce single-celled diploid spores that grow into adults themselves. (2) Sexual sporulation, whereby adult organisms produce single-celled diploid spores that divide into haploid gametes. The haploid gametes enter a haploid "pool", where they may recombine with other haploids to form a diploid spore that then grows into an adult. We consider a haploid fusion rate given by second-order reaction kinetics. We work with a simplified model where the diploid genome consists of only two chromosomes, each of which may be rendered defective with a single point mutation of the wild-type. We find that the asexual strategy is favored when the rate of spore production is high compared to the characteristic growth rate from a spore to a reproducing adult. Conversely, the sexual strategy is favored when the rate of spore production is low compared to the characteristic growth rate from a spore to a reproducing adult. As the characteristic growth time increases, or as the population density increases, the critical ratio of spore production rate to organism growth rate at which the asexual strategy overtakes the sexual one is pushed to higher values. Therefore, the results of this model suggest that, for complex multicellular organisms, sexual replication is favored at high population densities, and low growth and sporulation rates.Comment: 8 pages, 5 figures, to be submitted to Journal of Theoretical Biology, figures not included in this submissio

Stock Market Liquidity And Dividend Policy In Korean Corporations

The liquidity hypothesis predicts a negative relationship between stock liquidity and dividend payout propensity, i.e., a firm will decide to pay dividends to compensate for the liquidity demand of investors. This study comprehensively examines whether the liquidity hypothesis applies to the sample of Korean firms listed in the KOSPI and KOSDAQ markets. The main results of this paper are as follows. First, the dividend policy in Korean firms does not support the liquidity hypothesis, contradictory to the existing empirical studies. Next, the explanatory power of the liquidity hypothesis is even weaker for the KOSDAQ market, inconsistent with international evidence. Finally, even when we focus on the firm-year observations with non-negligible dividend payments, the liquidity hypothesis does not explain the dividend policy of Korean firms either. Our findings significantly contribute to the literature by robustly confirming the very limited role of the liquidity hypothesis for Korean financial markets. 

Heterogeneous Multi-Layered Network Model for Omics Data Integration and Analysis

Advances in next-generation sequencing and high-throughput techniques have enabled the generation of vast amounts of diverse omics data. These big data provide an unprecedented opportunity in biology, but impose great challenges in data integration, data mining, and knowledge discovery due to the complexity, heterogeneity, dynamics, uncertainty, and high-dimensionality inherited in the omics data. Network has been widely used to represent relations between entities in biological system, such as protein-protein interaction, gene regulation, and brain connectivity (i.e. network construction) as well as to infer novel relations given a reconstructed network (aka link prediction). Particularly, heterogeneous multi-layered network (HMLN) has proven successful in integrating diverse biological data for the representation of the hierarchy of biological system. The HMLN provides unparalleled opportunities but imposes new computational challenges on establishing causal genotype-phenotype associations and understanding environmental impact on organisms. In this review, we focus on the recent advances in developing novel computational methods for the inference of novel biological relations from the HMLN. We first discuss the properties of biological HMLN. Then we survey four categories of state-of-the-art methods (matrix factorization, random walk, knowledge graph, and deep learning). Thirdly, we demonstrate their applications to omics data integration and analysis. Finally, we outline strategies for future directions in the development of new HMLN models

Small molecule modulation of microbiota: a systems pharmacology perspective

Background Microbes are associated with many human diseases and influence drug efficacy. Small-molecule drugs may revolutionize biomedicine by fine-tuning the microbiota on the basis of individual patient microbiome signatures. However, emerging endeavors in small-molecule microbiome drug discovery continue to follow a conventional “one-drug-one-target-one-disease” process. A systematic pharmacology approach that would suppress multiple interacting pathogenic species in the microbiome, could offer an attractive alternative solution. Results We construct a disease-centric signed microbe–microbe interaction network using curated microbe metabolite information and their effects on host. We develop a Signed Random Walk with Restart algorithm for the accurate prediction of effect of microbes on human health and diseases. With a survey on the druggable and evolutionary space of microbe proteins, we find that 8–10% of them can be targeted by existing drugs or drug-like chemicals and that 25% of them have homologs to human proteins. We demonstrate that drugs for diabetes can be the lead compounds for development of microbiota-targeted therapeutics. We further show that the potential drug targets that specifically exist in pathogenic microbes are periplasmic and cellular outer membrane proteins. Conclusion The systematic studies of the polypharmacological landscape of the microbiome network may open a new avenue for the small-molecule drug discovery of the microbiome. We believe that the application of systematic method on the polypharmacological investigation could lead to the discovery of novel drug therapies

Meta-synthesis of studies on self-stigma in chronic disease

The purpose of this study was to synthesize the concept of self-stigma in patients who have chronic disease and to classify the its attributes systematically

Loss of aquaporin-1 expression is associated with worse clinical outcomes in clear cell renal cell carcinoma: an immunohistochemical study

Background Aquaporin (AQP) expression has been investigated in various malignant neoplasms, and the overexpression of AQP is related to poor prognosis in some malignancies. However, the expression of AQP protein in clear cell renal cell carcinoma (ccRCC) has not been extensively investigated by immunohistochemistry with large sample size. Methods We evaluated the AQP expression in 827 ccRCC with immunohistochemical staining in tissue microarray blocks and classified the cases into two categories, high and low expression. Results High expression of aquaporin-1 (AQP1) was found in 320 cases (38.7%), but aquaporin-3 was not expressed in ccRCC. High AQP1 expression was significantly related to younger age, low TNM stage, low World Health Organization/International Society of Urologic Pathology nuclear grade, and absence of distant metastasis. Furthermore, high AQP1 expression was also significantly associated with longer overall survival (OS; p<.001) and progression-specific survival (PFS; p<.001) and was an independent predictor of OS and PFS in ccRCC. Conclusions Our study revealed the prognostic significance of AQP1 protein expression in ccRCC. These findings could be applied to predict the prognosis of ccRCC

Portal flow steal after liver transplantation

Portal flow steal occasionally persists even after the liver transplantation, which may reduce the portal flow and thus threaten the patients' outcome. Therefore, pre- and peri-operative detection of portal steal phenomenon requiring radiological or surgical interruption is essential for the liver transplantation candidates as well as for the recipients

New York City House Mice (Mus musculus) as Potential Reservoirs for Pathogenic Bacteria and Antimicrobial Resistance Determinants

House mice (Mus musculus) thrive in large urban centers worldwide. Nonetheless, little is known about the role that they may play in contributing to environmental contamination with potentially pathogenic bacteria. Here, we describe the fecal microbiome of house mice with emphasis on detection of pathogenic bacteria and antimicrobial resistance genes by molecular methods. Four hundred sixteen mice were collected from predominantly residential buildings in seven sites across New York City over a period of 13 months. 16S rRNA sequencing identified Bacteroidetes as dominant and revealed high levels of Proteobacteria. A targeted PCR screen of 11 bacteria, as indicated by 16S rRNA analyses, found that mice are carriers of several gastrointestinal disease-causing agents, including Shigella, Salmonella, Clostridium difficile, and diarrheagenic Escherichia coli. Furthermore, genes mediating antimicrobial resistance to fluoroquinolones (qnrB) and β-lactam drugs (blaSHV and blaACT/MIR) were widely distributed. Culture and molecular strain typing of C. difficile revealed that mice harbor ribotypes associated with human disease, and screening of kidney samples demonstrated genetic evidence of pathogenic Leptospira species. In concert, these findings support the need for further research into the role of house mice as potential reservoirs for human pathogens and antimicrobial resistance in the built environment

Clinical impact of collateral circulation in patients with median arcuate ligament syndrome

PURPOSE:We aimed to analyze computed tomography (CT) findings and medical records of patients diagnosed with median arcuate ligament syndrome (MALS) and evaluate possible risk factors associated with vascular complications that develop in patients with MALS.METHODS:This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. A total of 37 consecutive patients were diagnosed with MALS using both axial and sagittal CT reconstruction imaging at a single institution over a 7-year period. Dynamic contrast-enhanced CT data, medical records, and angiography results were reviewed.RESULTS:Thirty-two (86.5%) patients were asymptomatic and incidentally diagnosed with MALS using CT. Seventeen (45.9%) patients exhibited significant arterial collateral circulations and nine (24.3%) were found to have splanchnic artery aneurysms, including one (2.7%) with acute bleeding secondary to aneurysm rupture. Peripancreatic vascular network including pancreaticoduodenal arcades and dorsal pancreatic artery was the most common site for development of both collateral circulations (16/22, 72.7%) and aneurysms (9/16, 56.3%). Splanchnic artery aneurysms were significantly more common in patients with collateral circulations (8/17, 47.1%) compared with those without collateral circulations (1/20, 5%) (P < 0.01). At least one peripancreatic vascular aneurysm was found in five of nine patients with splanchnic artery aneurysms (55.6%).CONCLUSION:Splanchnic artery aneurysms are not uncommon in asymptomatic patients with collateral circulations caused by significant celiac trunk stenosis or obstruction due to median arcuate ligament. Therefore, careful imaging evaluation is necessary in patients with peripancreatic collateral circulations associated with MALS and regular follow-up is recommended for possibility of aneurysm development and rupture. Prophylactic endovascular treatment should be specifically performed in patients with pancreaticoduodenal arcade aneurysms to prevent life-threatening aneurysm rupture regardless of size

Multimodality imaging studies of intraductal tubulopapillary neoplasms of the pancreas

PURPOSEWe aimed to investigate multimodality imaging findings of intraductal tubulopapillary neoplasms (ITPN) of the pancreas.METHODSThis study was approved by the institutional review board with waived informed consent. A total of eight patients were histopathologically diagnosed with pancreatic ITPN in a single institution over a 6-year period. The imaging findings of dynamic contrast-enhanced computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasonography (EUS), and positron emission tomography-computed tomography (PET-CT) were reviewed and correlated with clinicopathologic findings.RESULTSHistopathologically, an invasive carcinoma component was found in 5 of 8 patients (62.5%). The median diameter of the lesions and the main pancreatic ducts were larger in ITPN with invasive carcinoma (19 mm, 13.3–98.0 mm and 13 mm, 5.9–16.3 mm, respectively) than in ITPN without invasive carcinoma (13 mm, 12.7–18.5 mm and 6 mm, 5.6–6.1 mm, respectively), but not significantly (lesions, P = 0.229 and main pancreatic ducts, P = 0.143). Pancreatolithiasis accompanied invasive carcinoma in 3 of 5 patients (60%). Intraductal solid tumors were demonstrated on CT (5/8, 62.5%), MRCP (5/7, 71.4%), and EUS (7/7, 100%). In addition, various imaging findings mimicking chronic autoimmune pancreatitis or pancreatic ductal adenocarcinoma were found in 3 patients (37.5%) on multimodality imaging. The lesion multiplicity and synchronous or metachronous biliary cancer occurred in 3 patients (37.5%), respectively.CONCLUSIONPatients with associated invasive carcinoma from pancreatic ITPN may have presented a trend toward larger tumor size and dilated pancreatic duct with pancreatoliths, but the difference was not statistically significant. Further studies with a larger number of patients are needed to provide better insight into these findings. Pancreatic ITPN can show various atypical imaging findings as well as typical intraductal solid tumor on multimodality imaging. The presence of lesion multiplicity and synchronous or metachronous biliary cancer can be helpful for assisting with the diagnosis of pancreatic ITPN